Sputtering is the use of ions produced by ion sources to accelerate the aggregation into high-speed ion flow in the vacuum to bombard the solid surface, so that the atoms on the solid surface leave the target material and deposit on the substrate surface, thus forming nano to micron thin films. The solid bombarded is called the sputtering target material. Sputtering coating is a basic means to prepare functional films in the fields of integrated circuits, flat panel displays (including liquid crystal displays and touch screens), thin film solar cells and light emitting diodes (LED), and sputtering target has become an indispensable basic material in these fields.
With the continuous improvement of the comprehensive performance of electronic products and the application environment, the performance of sputtering target is also put forward higher and higher requirements. Although molybdenum is an ideal electrode and wiring material for flat displays, thin film solar cells, and as a barrier material for semiconductors, it has been found to have problems with corrosion resistance (discoloration) and densivity (stripping of the film) in its applications. Research and practice show that adding niobium and other alloy elements to molybdenum sputtering target material can make the sputtering film after sputtering performance balance, such as specific impedance, stress, corrosion resistance, etc., more and more popular.
Molybdenum-niobium alloy can be made by smelting casting process, that is, a certain proportion of molybdenum and niobium raw materials are melted, and then the alloy molten liquid is poured into the mold, the ingot is obtained, and then the target material is made by heat treatment, forging, extrusion and rolling. The defects of this process lie in the shrinkage of the ingot, the coarse grain of the ingot, the poor uniformity of the composition, and the requirements of the process equipment are high.
Molybdenum-niobium alloy can also be prepared by powder metallurgy process. At present, there are many specific processes in powder metallurgy. The first process is to mix a certain amount of molybdenum powder and niobium powder, then press forming and vacuum sintering to get ingots. The disadvantage of this process lies in the difficulty of volatilizing oxygen impurities in molybdenum powder and niobium powder, which prevents sintering densification, and the relative density of ingots obtained is only 80-89%. Its improved version of the ingot by forging or rolling processing, but the process is complex, the yield is not high; The second process is to mix a certain amount of molybdenum powder and niobium powder, after forming by vacuum hot pressing or hot isostatic pressing to obtain the ingot, the relative density of the obtained ingot can reach 90-97%, but because of the need to use graphite mold, the equipment is complex, expensive, and easy to carburize; The third process is to mix a certain amount of molybdenum powder and niobium powder, after pressing forming and sintering, and then through hot isostatic pressing to obtain ingot, the relative density of the ingot can reach more than 98%, the shortcomings are long process, complex operation, high cost.
